According to the invention, there is provided a novel soybean variety designated RJS31004. This invention thus relates to the seeds of soybean variety RJS31004, to the plants of soybean RJS31004 to plant parts of soybean variety RJS31004 and to methods for producing a soybean plant produced by crossing plants of the soybean variety RJS31004 with another soybean plant, using RJS31004 as either the male or the female parent.